Who is the only resident Ditto initially meets in Pokémon Pokopia?

Tangrowth is the only resident Ditto initially meets in Pokémon Pokopia.

When Ditto awakens, the world has withered and humans are gone. Tangrowth lives alone in the wasteland and becomes the first important Pokémon character encountered by the player. The character later becomes known as Professor Tangrowth.

Professor Tangrowth helps explain the state of the world and encourages Ditto to restore Pokémon habitats. As those habitats improve, more Pokémon return, assist with tasks, and teach Ditto useful moves. This progression gives the building systems a story purpose: rebuilding the environment also brings life back to it.

Slowpoke and Onix are also involved in the plot, but they are encountered later and are not the first resident. Bulbasaur is connected to the Leafage move, yet it is not the solitary Pokémon found at the start.